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Accessory Chromosome Contributes to Virulence of Banana Infecting Fusarium oxysporum Tropical Race 4

Summary

Fusarium wilt Tropical Race 4 is a devastating fungal disease that destroys banana crops worldwide, particularly the commercially important Cavendish variety. Researchers discovered that this fungus carries a special accessory chromosome that is not essential for basic fungal survival but is critical for its ability to infect and damage banana plants. By removing this chromosome in laboratory studies, scientists found that infected bananas suffered significantly less damage, suggesting that understanding this chromosome could lead to better strategies for protecting banana crops from this destructive disease.

Background

Filamentous fungi have evolved compartmentalized genomes with conserved core regions and dynamic accessory regions that drive adaptation to changing environments. Tropical Race 4 (TR4) of Fusarium oxysporum causes devastating Fusarium wilt epidemics in Cavendish banana cultivars. Recent studies revealed that TR4 contains an accessory chromosome 12 (AC12) that undergoes extensive internal duplications in some strains, but the contribution of this chromosome to virulence remains unknown.

Objective

To determine the role of accessory chromosome 12 in the virulence of banana-infecting Fusarium oxysporum Tropical Race 4 and to understand the phenotypic effects of chromosome loss and structural rearrangements.

Results

AC12 was dispensable for vegetative growth but essential for full virulence, with AC12 loss mutants showing 48.9% corm necrosis compared to 95% in the parental strain. Loss of AC12 co-occurred with interchromosomal rearrangements of core chromosomes but without detectable growth defects. AC12 contributed to tolerance against high salt and cell wall stresses, and strains with or without intrachromosomal AC12 duplications showed similar virulence levels.

Conclusion

The independent accessory chromosome 12 significantly contributes to virulence of banana-infecting Fusarium oxysporum TR4, despite being dispensable for vegetative growth. The observed intrachromosomal duplications and chromosomal rearrangements indicate high genome plasticity in this fungal pathogen. Further understanding of AC12 function and dynamics will be crucial for developing strategies to combat this devastating banana pathogen.
  • Published in:Molecular Plant Pathology,
  • Study Type:Experimental Study,
  • Source: 10.1111/mpp.70146, PMID: 40939022
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